1. Field of the Invention
The present invention relates to an ink jet recording apparatus which relatively moves a carriage on which an ink jet head is mounted to a recording medium and performs recording and an ink detection method in the pertinent apparatus.
2. Related Background Art
Various recording apparatuses which perform recording on recording media such as paper and sheets for an OHP (overhead projector) are proposed up to this date. Among them, an ink jet recording apparatus directly injects ink from a recording head to recording paper, and is used as a recording apparatus which has advantages of low running costs and quiet recording operation.
In an ink jet recording apparatus, various methods which detect the presence of ink of an ink tank (ink cartridge) installed in an ink jet head are proposed. For example, there is a method of using a photo-interrupter equipped with a light emitting element and a light reception element to eject an ink droplet between the light emitting element and light reception element of the photo-interrupter, detecting whether an optical axis between the light emitting element and light reception element was intercepted or not based on the output of the photo-interrupter, and judging whether the ink was normally ejected or not, otherwise the presence of the ink.
On the other hand, in order to detect whether ink was normally ejected or not, otherwise the presence of the ink, there is also a method of judging the presence of remaining ink amount according to whether a mark for detecting the presence of the ink is printed on a recording medium and its detection mark is appropriately printed by a reflection-type photosensor.
However, among the conventional methods, the former method ejects ink between photosensors. In that case, if the configuration is used in which the ink is ejected by once moving an ink jet head between the photosensors and stopping it there, there is a problem that accurate detection cannot be performed when the ink cannot be ejected on the optical axis of a photo-interrupter with good accuracy. In particular, along with an improvement of the resolution of an ink jet recording apparatus in recent years, the liquid droplet of the ink to be ejected is reduced. As an ink droplet is reduced, it becomes difficult to eject the ink droplet on the optical axis of the photo-interrupter with good accuracy. To resolve such problem, the configuration is considered in which ink is detected by moving a recording head ejecting the ink in the vicinity of the optical axis of the photo-interrupter and allowing the ink droplet to cross the optical axis by the ejection while the recording head is moving.
However, in a color ink jet recording apparatus which records a color image by ejecting a plurality of color inks, since light shielding characteristics for a photo-interrupter are different from each other according to the color difference in each of the plurality of color inks, there is a problem that the reliability of a decision result is decreased when each color ink is detected in the same sequence. Moreover, in recent years, to improve gradation, the configuration is also proposed in which recording is performed using a plurality of inks having different density in the same color. Since light shielding characteristics differ in the ink having such different density, a problem will occur in which the reliability of a decision result is decreased in the same manner as the color inks if the inks are detected in the same sequence.
Further, in the latter system which detects a recorded mark, while its detection accuracy is high, a mark must be recorded on a recording medium independently of the information to be recorded actually to detect the presence of ink. Accordingly, there are problems that an originally unnecessary mark will be recorded on the recording medium as a recording result or the recording medium will be used wastefully. In this case, a sensor for reading the mark with high accuracy is necessary.
The present invention is intended in consideration of the above conventional examples, and an object of the present invention is to provide an ink jet recording apparatus which enables decision of the presence of ink ejection with good accuracy regardless of ink colors and an ink detection method in the pertinent apparatus.
To attain the above object, an ink jet recording apparatus according to the present invention comprises the following configuration.
That is, an ink jet recording apparatus which performs recording on a recording medium by ejecting inks of a plurality of different colors by the use of an ink jet head for ejecting the inks, comprises moving means for moving the ink jet head to the recording medium, detecting means, installed at a predetermined position within the moving area of the ink jet head by the moving means, for detecting the inks ejected from the ink jet head and outputting a detection signal in accordance with a detection result, ink ejecting means for moving the ink jet head by the moving means and ejecting the inks from the ink jet head within the predetermined area including the predetermined position, deciding means for deciding the presence of ink ejection by the ink ejecting means on the basis of a detection signal output from the detecting means, and control means for changing at least one condition of the ink ejection cycle by the ink ejecting means, the moving speed of the ink jet head by the moving means and the number of the inks ejected within the predetermined area by the ink ejecting means, in accordance with the colors of the inks.
Further, to attain the above object, an ink detection method in an ink jet recording apparatus of the present invention comprises the following steps.
That is, an ink detection method in an ink jet recording apparatus which performs recording on a recording medium by ejecting inks of a plurality of different colors by the use of an ink jet head for ejecting the inks comprises a moving step of moving the ink jet head to detecting means, installed at a predetermined position within an area to which the ink jet head is moved, for detecting the inks ejected from the ink jet head and outputting a detection signal in accordance with a detection result, an ink ejecting step of ejecting the inks from the ink jet head when the ink jet head is located in the predetermined area including the predetermined position during the moving of the ink jet head in the moving step, and a deciding step of deciding the presence of ink ejection by the ink ejecting means on the basis of the detection signal output by the detecting means, at least one condition of the ink ejection cycle by the ink ejecting means, the moving speed of the ink jet head by the moving means and the number of the inks ejected within the predetermined area by the moving means being changed, in accordance with the colors of the inks.
Further, an ink jet recording apparatus of the present invention is directed to an ink jet recording apparatus which performs recording on a recording medium by ejecting a plurality of inks which differ in light shielding characteristics, said ink jet recording apparatus comprises, a carriage equipped with an ink jet head for ejecting the inks, main scanning means for scanning the ink jet head mounted on the carriage by scanning the carriage to the recording medium along a main scanning direction, detecting means which is located at a predetermined position within the scanning area of the ink jet head scanned by the main scanning means and which comprises light emitting means for emitting light in a direction different from the main scanning direction and light reception means for receiving the light emitted by the light emitting means and which outputs a signal according to whether or not an optical axis formed between the light emitting means and the light reception means is intercepted, ejection control means for scanning the ink jet head by the scanning means and for ejecting the ink from the ink jet head within the predetermined area including the optical axis of the detecting means, deciding means for deciding the presence of ink ejection by the ejection control means on the basis of a detection signal output from the detecting means, and control means for changing at least one condition of the ejection cycle of the ink ejected by the ejection control means, the scanning speed of the ink jet head by the main scanning means, a position of the start of the ink ejection by the ejection control means and the number of inks ejected within the predetermined area by the ejection control means, in accordance with the light shielding characteristics of the inks ejected by the ejection control means among the plurality of different inks.
Furthermore, the present invention is an ink detection method in an ink jet recording apparatus which moves an ink jet head for ejecting ink to a recording medium and which performs recording on the recording medium by ejecting a plurality of inks different in light shielding characteristics, and said ink detection method comprises, a moving step of moving the ink jet head to detecting means which is located at a predetermined position within an area to which the ink jet head is moved and which comprises light emitting means for emitting light and light reception means for receiving the light and which outputs a signal according to whether or not an optical axis formed between the light emitting means and the light reception means is intercepted, an ink ejecting step of ejecting the ink from the ink jet head when the ink jet head is located within the predetermined area including the predetermined position during the moving of the ink jet head in the moving step, and a deciding step of deciding the presence of ink ejection by the ink ejecting means on the basis of the detection signal output by the detecting means, wherein at least one condition of the ejection cycle of the ink ejected by the ink ejecting means, the travel speed of the ink jet head, the position of the start of the ink ejection by the ink ejecting means and the number of the inks ejected within the predetermined area by the ink ejecting means are changed in accordance with the light shielding characteristics of the ink.